When you light a candle, the paraffin wax soon begins to melt. Paraffin wax is a covalent compound. Can you classify the melting of the wax as a chemical change or a physical change? If so, which is it? If you cannot classify it as chemical or physical, explain why not. Justify your answer by describing the forces involved in the change.
I am not sure how to answer this because while the burning of the candle is chemical, melting is just a physical change...
I think you should write it down as a physical change because here they are asking about the wax and not the thread or string in the middle.
Paraffin wax is a covalent compound, so when it melts the molecules simply pull away from each other, leaving the bonds intact, because of this Parffin wax melting is a physical change.
Well, you've stumbled upon a classic wax on, wax off situation here! Let's break it down, shall we?
Melting paraffin wax is indeed a physical change, not a chemical change. The lovely process of melting is all about getting those molecules to loosen up and transition from a solid to a liquid state. No major bond-breaking or bond-making is happening during this process.
In the case of paraffin wax, it's made up of long, tangled chains of hydrocarbon molecules held together by weak intermolecular forces, like London dispersion forces. When you apply heat, those forces start to take a chill pill, allowing the wax molecules to slide past each other and transform into a gooey liquid.
Just like watching ice cream melt on a hot day, the melting of wax is reversible – you can easily solidify it again by removing the heat. So, it's purely a physical transformation, no chemical shenanigans involved. Keep calm and melt on!
You're right! The burning of a candle involves a chemical change, as it results in the combustion of the wax and the release of heat, light, and carbon dioxide. However, the melting of the wax can be classified as a physical change.
A physical change refers to a transformation in the physical properties of a substance, where no new substance is formed. In the case of melting, the paraffin wax undergoes a phase change from a solid to a liquid state, but the chemical composition of the wax remains the same.
During melting, the intermolecular forces holding the molecules of the paraffin wax together are overcome by the input of heat energy. Paraffin wax is composed mainly of hydrocarbon molecules, which are linked by weak dispersion forces, also known as London dispersion forces. These forces are relatively weak and easily disrupted by heat.
When heat is applied to the solid wax, its molecules start to gain kinetic energy, increasing their vibrational motion. Eventually, this causes the molecules to break free from their fixed positions in the solid lattice, resulting in the conversion of solid wax to liquid wax. While the phase of the substance changes, the individual molecules of paraffin wax remain the same before and after melting.
In summary, the melting of paraffin wax is a physical change because it involves a phase transition from solid to liquid, without any alteration in the chemical composition or identity of the wax.